591 research outputs found
Author ID’s: enhance visibility and accessibility: Workshop 2
No full textPapers presented at the second workshop on Author ID’s: enhance visibility and accessibility , Auditorium, Merensky Library, University of Pretoria, 28 October 2015Follow up on the first workshop (Researcher ID Workshop), the aim of this workshop was to continue discussion on the information specialists' role in enhancing research visibility and accessibility. A large part of the workshop was devoted to a discussion and practical demonstration of ORCID ID by Mr Matthew Buys, the Regional Director of ORCID. Author IDs were also discussed from different perspectives, including a junior information specialist (Ms Lesego Makhafola); a cataloguer (Ms Martha De Waal); a researcher (Prof. Estelle Venter) and a case study at GIBS (Ms Beulah Muller).mn201
Die rol van kognitiewe funksionering in hoop by adolessente
No full textEnglish: The primary aim of this research was to clarify the cognitive function of hope in
adolescents. The hope construct was theoretically investigated in this research and
an integrated hope model and hope process were developed. The nature of hope
was investigated in adolescents (boys and girls respectively). Hope is furthermore
described (for the purpose of this study) as a mood condition which activates
emotions. A cognitive process starts when pathway thoughts (the setting of
objectives) and work agency thinking (motivation) take place. Cognitive function in
hope is discussed by means of describing cognitive styles. The connection between
cognitive styles and hope is further investigated and also related to cognitive
development in adolescents. Specific attention is paid to hope and the adolescent
in the South African context.
During the empirical study, the cluster sampling method was used to identify four
schools in the North West Province which would participate in this research. All the
grade 12 learners of those specific schools were approached to complete
questionnaires. The study group consisted of 485 adolescents. In this research,
hope was determined by the Hope Scale of Snyder et al. (1991a) and cognitive
function by means of the Constructed Thinking Inventory (Epstein, 1993) and the
Cognitive Flexibility Scale (Martin & Rubin, 1995), respectively. Good reliability
indices were obtained for all the questionnaires and scales used.
Five variables, namely cognitive flexibility, naïve optimism, esoteric thinking,
personal beliefs (superstition) and behaviour coping, contribute considerably to the
clarification of the variance of the pathway component of hope in adolescents.
As far as culture and cognitive functioning were concerned, definite differences
between score averages were obtained on four scales of the two culture groups.
These scales were global constructive thinking, esoteric thinking, naïve optimism
and cognitive flexibility.
Afrikaans-speaking adolescents obtained a higher average score than the Africanlanguage
adolescents on the scale of global constructed thinking. Concerning the
scales of esoteric thinking, naïve optimism, and cognitive flexibility the Africanlanguage
adolescents obtained a higher average score than the Afrikaans-speaking
adolescents. The higher average score of the African-language adolescents
indicates lower cognitive flexibility. However, it is important to take into account
that the cognitive flexibility scale is based on western culture.
Despite the fact that the biographical variable, culture, does not considerably
contribute to the clarification of the pathway component variance, it does contribute
to the clarification of the agency component variance.
As far as gender differences are concerned, the results of this study give no
indication of any contribution to the clarification of the variance of the agency or the
pathway components of hope. Obvious differences were evident concerning the
average emotional coping and naïve optimism of the two sexes. Concerning the
emotional-coping scale, the boys obtained a higher average score than the girls,
while the girls obtained a higher average score than the boys on the scale naïve
optimism.
Recommendations for further research were made on the strength of the results.Afrikaans: Die primêre doel van hierdie navorsing was om kognitiewe funksie in hoop by
adolessente te verklaar. Die konstruk hoop is in hierdie navorsing teoreties
ondersoek en 'n geïntegreerde hoopmodel, asook 'n geïntegreerde hoopproses is
ontwikkel. Die aard van hoop is by adolessente (onderskeidelik seuns en dogters)
ondersoek. Verder is hoop is vir die doeleindes van hierdie studie as 'n
gemoedstoestand beskryf wat emosies aktiveer. 'n Kognitiewe proses tree in
werking wanneer fasiliteringsbaandenke (die stel van doelwitte) en werkbaandenke
(motivering) plaasvind. Kognitiewe funksie in hoop is bespreek deur die beskrywing
van kognitiewe style. Die verband tussen kognitiewe style en hoop is verder
aangedui en ook in verband gebring met kognitiewe ontwikkeling by adolessente.
Daar is spesifiek gelet op hoop en die adolessent in die Suid-Afrikaanse konteks.
In die empiriese ondersoek is van die trossteekproeftrekkingsmetode gebruik
gemaak om vier skole in die Noordwes-Provinsie te identifiseer, wat aan die
navorsing sou meedoen. AI die graad 12-leerders van daardie spesifieke skole is
genader om vraelyste te voltooi. Die ondersoekgroep het bestaan uit 485
adolessente. In hierdie navorsing is hoop bepaal deur die hoopskaal van Snyder et
al. (1991) en kognitiewe funksie deur onderskeidelik die Kognitiewe denkevraelys
(Epstein, 1993) en die Kognitiewe buigsaamheidsvraelys (Martin & Rubin, 1995).
Goeie betroubaarheidsindekse is vir al die vraelyste en skale wat gebruik is, verkry.
Vyf veranderlikes, naamlik kognitiewe buigsaamheid, naïewe optimisme, esoteriese
denke, persoonlike bygelowige denke en gedrags-coping, lewer 'n beduidende
bydrae tot die verklaring van die variansie van die fasiliteringsbaankomponent in
hoop van adolessente.
Met betrekking tot kultuur en kognitiewe funksionering, is beduidende verskille
tussen die gemiddelde tellings op vier skale vir die twee kultuurgroepe verkry.
Hierdie skale is globale konstruktiewe denke, esoteriese denke, naïewe optimisme
en kognitiewe buigsaamheid.
Ten opsigte van globale konstruktiewe denke het die Afrikaanssprekendes 'n hoër
gemiddelde telling as die Afrikataalsprekendes verkry. Wat die skale esoteriese
denke, naïewe optimisme en kognitiewe buigsaamheid betref, toon die
Afrikataalsprekendes telkens 'n hoër gemiddelde telling as die Afrikaanssprekendes.
Die hoër gemiddelde telling wat die Afrikataalsprekendes in vergelyking met die
Afrikaanssprekendes behaal het op die skaal kognitiewe buigsaamheid is
aanduidend van laer kognitiewe buigsaamheid. Dit behoort egter in ag geneem te
word dat die kognitiewe buigsaamheidskaal vir die westerse kultuur ontwikkel is.
Hoewel die biografiese veranderlike, kultuur, nie beduident bydra tot die verklaring van die variansie van die fasiliteringsbaankomponent nie, dra kultuur wel by tot die verklaring van variansie van die werkbaankomponent.
Wat geslagsverskille betref, toon die resultate van hierdie studie geen bydrae tot die
verklaring van die variansie van die werkbaankomponent sowel as van die
fasiliteringsbaankomponent in hoop nie. Beduidende verskille is egter ten opsigte
van die gemiddelde tellings vir emosionele coping en naïewe optimisme vir die twee
geslagte verkry. Ten opsigte van die emosionele-copingskaal het die seuns 'n hoër
gemiddelde telling as die dogters behaal, terwyl wat naïewe optimisme betref, die
dogters weer 'n hoër gemiddelde telling as die seuns behaal het.
Uit die resultate is aanbevelings vir verdere navorsing gemaak
Phenolic composition and in vitro antioxidant capacity of South African plums (Prunus salicina Lindl.)
No full textThesis (MSc Food Sc)--Stellenbosch University, 2013.ENGLISH ABSTRACT: Phenolic compounds of the types present in plums have been found to exhibit health-promoting properties associated with their antioxidant capacity. Fruits with red peel and/or flesh are thus sought-after for their high antioxidant levels. In the current study South African plum (Prunus salicina Lindl.) cultivars and selections, harvested during two consecutive fruit seasons, were compared in terms of general fruit attributes (colour, firmness, °Brix, pH, titratable acidity), phenolic composition and antioxidant capacity. The effect of season and a commercial cold storage and ripening regime was also investigated.
A reversed-phase high-performance liquid chromatography-diode-array-fluorescence detection (HPLC-DAD-FLD) method suitable for use with mass spectrometry (MS) detection, was optimised for separation and identification of phenolic compounds from four phenolic groups (phenolic acids, anthocyanins, flavan-3-ols and flavonols) in six South African plum cultivars and five selections. Parameters that were optimised include the mobile phases, analysis temperature and gradient program. Good stability, linearity and inter- and intra-day precision were obtained. Identification of compounds was based on comparison of retention times, UV-Vis spectra and mass fragments with available authentic phenolic standards and/or literature data. The optimised method allowed identification or tentative identification of twenty-four phenolic compounds, including cyanidin-3-O-glycosides, quercetin glycosides, monomeric, dimeric and trimeric flavan-3-ols, and hydroxycinnamic acids. An on-line ABTS•+ (2,2ʹ-azinobis-(3-ethyl-benzothiazoline-6-sulfonic acid)) antioxidant assay, performed for qualitative evaluation of the antioxidant response of individual phenolic compounds, indicated the flavan-3-ols as major antioxidants in plums.
Eighteen phenolic compounds were quantified, including anthocyanins and flavonol glycosides, flavan-3-ols (monomers and dimers) and hydroxycinnamic acids. Phenolic composition differed greatly between cultivars and selections. Cyanidin-3-O-glucoside was the predominant anthocyanin in plums with red peel and/or flesh, followed by cyanidin-3-O-rutinoside. Cyanidin-3-O-galactoside was present only in the cultivar Laetitia (red peel, yellow flesh). The ripe fruit of Ruby Red and PR04-19, both with red peel and flesh, had the highest anthocyanin content for the first and second harvest season, respectively. Neochlorogenic acid and quercetin-3-O-glucoside were the major phenolic acid and flavonol, respectively. Chlorogenic acid, 3-O-p-coumaroylquinic acid and several quercetin-glycosides and -diglycosides were also present in some cultivars and selections. Procyanidin B1 was the flavan-3-ol present in the highest concentration in the majority of cultivars and selections and its content correlated with the (+)-catechin content, while the same was observed for procyanidin B2 and (-)-epicatechin.
The effect of cold storage and ripening on fruit attributes differed greatly between cultivars and selections. The increase and decrease in pH and titratable acidity, respectively, were as expected for ripe fruit as opposed to unripe fruit. Ripe fruit had higher a*-values and lower L*-values. The cold storage and ripening regime had no significant effect on total polyphenol and total flavan-3-ol content of the cultivars and selections, but the anthocyanin content increased in some cases.
In terms of in vitro antioxidant capacity, the selections PR04-32 and PR04-35, both with red peel and flesh, had the highest antioxidant capacity, irrespective of assay. Sapphire (red peel, yellow flesh), with the lowest total polyphenol content, also had the lowest antioxidant capacity in the ORAC and FRAP assays. Both the total polyphenol and flavan-3-ol contents correlated significantly to antioxidant capacity, irrespective of assay.AFRIKAANSE OPSOMMING: Fenoliese verbindings, soos teenwoordig in pruime, is bekend vir hul gesondheidsbevorderende eienskappe wat geassosieer word met antioksidant kapasiteit. Vrugte met ‘n rooi skil en/of vleis is veral gesog as gevolg van hul hoë antioksidant aktiwiteit. Met hierdie studie is Suid-Afrikaanse pruim (Prunus salicina Lindl.) kultivars en seleksies, geoes tydens twee opeenvolgende seisoene, vergelyk in terme van algemene vrug einskappe (kleur, fermheid, °Brix, pH en titreerbare suurheid), fenoliese samestelling en antioksidant kapasiteit. Die effek van ‘n kommersiële koelopberging en rypwording prosedure is ook ondersoek.
‘n Omgekeerde-fase hoë-druk vloeistof chromatografie (HPLC) metode met diode-opstelling en fluoressensie deteksie, maar wat ook geskik is vir massa spektrometrie (MS), is geoptimiseer om fenoliese verbindings te skei en te identifiseer in Suid-Afrikaanse pruime. Verbindings van vier fenoliese groepe (fenoliese sure, antosianiene, flavan-3-ole en flavonole) wat in ses kultivars en vyf seleksies voorgekom het, is ondersoek. Die vloeistof fases, skeidingstemperatuur en gradiënt van die metode is geoptimiseer. Goeie resultate vir stabiliteit, lineariteit en inter- en intra-dag akkuraatheid is verkry. Verbindings is geïdentifiseer deur vergelyking van retensie tye, UV-Vis spektra en massa fragmente met dié van egte fenoliese standaarde en/of met literatuur data. Vier-en-twintig fenoliese verbindings is geïdentifiseer of voorlopig geïdentifiseer, insluitende sianidien- en kwersetien glikosiede, flavan-3-ol monomere, dimere en trimere, en hidroksikaneelsure. ‘n Aanlyn ABTS•+ (2,2 ʹ-azino-di-(3-etielbensotialosien-sulfoon suur) radikaal katioon blussingstoets is gebruik om die antioksidant reaksie van individuele polifenole op ‘n kwalitatiewe wyse te evalueer en flavan-3-ole is as hoof antioksidante in pruime aangetoon. Kwantifisering van agtien verbindings, insluitende antosianiene, flavonol glikosiede, flavan-3-ole (monomere en dimere) en hidroksikaneelsure, was moontlik met hierdie geoptimiseerde metode. Die fenoliese samestelling het aansienlik verskil tussen kultivars en seleksies. Sianidien-3-O-glukosied was die hoof antosianien in pruime met ‘n rooi skil en/of vleis, gevolg deur sianidien-3-O-rutinosied. Sianidien-3-O-galaktosied het slegs in Laetitia (rooi skil en geel vleis) voorgekom. Ryp vrugte van Ruby Red en PR04-19, beide met rooi skil en vleis, het onderskeidelik die hoogste antosianieninhoud gehad met die eerste en tweede seisoen se oeste. Neochlorogeniese suur en kwersetien-3-O-glukosied was die hoof fenoliese suur en flavon-3-ol, onderskeidelik. Chlorogeniese suur, 3-O-p-kumarienkwiniensuur en verskeie kwersetien glikosiede en diglikosiede was teenwoordig in sekere kultivars/seleksies. Die flavan-3-ol, prosianidien B1, was teenwoordig in die hoogste konsentrasie in die meerderheid kultivars/seleksies. Die prosianidien B1 inhoud het met die (+)-katekien inhoud gekorreleer, terwyl dieselfde gevind is vir prosianidien B2 en (-)-epikatekien.
Die effek van koelopberging en rypwording op die algemene vrug einskappe het tussen kultivars en seleksies verskil. Die pH en titreerbare suurheid het onderskeidelik toegeneem en afgeneem, soos verwag is vir ryp vrugte teenoor onryp vrugte. Ryp vrugte het hoër a*-waardes en laer L*-waardes getoon. Koelopberging en rypwording het geen beduidende effek op die totale polifenol- en totale flavan-3-ol inhoud gehad nie, maar die antosianieninhoud het vir sommige kultivars en seleksies toegeneem.
In terme van in vitro antioksidant kapasiteit het die seleksies PR04-32 en PR04-35, beide met rooi skil en vleis, die hoogste antioksidant kapasiteit getoon, ongeag die antioksidant toets wat gebruik is. Sapphire (rooi skil en geel vleis) het die laagste totale polifenolinhoud gehad, asook die laagste antioksidant kapasiteit soos bepaal deur die ORAC en FRAP toetse. Beide die totale polifenol- en flavan-3-ol inhoud het beduidend met die antioksidant kapasiteit korreleer, ongeag van die toets wat gebruik is.Master
Eben Venter as gewete van die vleiseters
No full textThis artide explores the representation of meat in three novels by Eben Venter, namely Foxtrot van die vleiseters (1993) (published in translation as Foxtrot of the Meat-Eaters), Ek stamel ek sterwe (2005) (published in translation as My Beautiful Death), and Horrelpoot (2006) (published in translation as Trencherman). The author uses the metaphor of meat and meat consumption to comment on the greed and oppression associated with the white farm owner and patriarch, as well as on other related issues such as gender, the body and sexuality. Finally the artide explores the use of vegetarianism as a counter-discourse by the author to undermine the prevalent meat-loving culture associated with the farm-novel tradition in Afrikaans. In all three novels there is an opposition between life on the farm and life in the big city, predominantly life in large Australian cities after the main characters have emigrated to Australia.
Opsomming Hierdie artikel ondersoek die simboliese uitbeelding van vleis in drie romans deur Eben Venter, naamlik Foxtrot van die vleiseters (1993), Ek stamel ek sterwe (2005) (in Engels gepubliseer as My Beautiful Death) en Horrelpoot (2006) (in Engels gepubliseer as Trencherman). Die auteur gebruik die metafoor van vleis en die eet of verbruik daarvan, om kommentaar te lewer op die gierigheid en onderdrukking wat verband hou met die blanke plaaseienaar en patriarg, sowel as ander verwante kwessies soos geslag, die liggaam en seksualiteit. Uiteindelik ondersoek die artikel ook die gebruik van vegetarisme as \u27n teendiskoers deur die auteur, om sodoende die dominante vleiseterkultuur, wat verband hou met die plaasromantradisie in Afrikaans, te ondermyn. In al drie romans is daar \u27n teestelling tussen die lewe op die plaas en die in die grootstad, hoofsaaklik in groat Australiese stede, nadat die hoofkarakters na Australie geemigreer het.
Replication kit for "Demand-and-Supply Imbalance Risk and Long-Term Swap Spreads" (2024) by Samuel G. Hanson, Aytek Malkhozov, Gyuri Venter
No full textThis is the replication kit for Hanson, Malkhozov, and Venter "Demand-and-Supply Imbalance Risk and Long-Term Swap Spreads". The corresponding author is Samuel Hanson, [email protected] DATASET IS ARCHIVED AT DANS/EASY, BUT NOT ACCESSIBLE HERE. TO VIEW A LIST OF FILES AND ACCESS THE FILES IN THIS DATASET CLICK ON THE DOI-LINK ABOV
Nutraceutical Value of Yellow- and Red-Fleshed South African Plums (Prunus salicina Lindl.): Evaluation of Total Antioxidant Capacity and Phenolic Composition
No full textTen South African plum cultivars and selections, including yellow- and red-fleshed plums from two harvest seasons were evaluated in terms of nutraceutical value (phenolic composition, total polyphenol content (TPC) and total antioxidant capacity (TAC)) and fruit attributes (colour, fruit mass, etc.). Plums were evaluated at two maturity stages, i.e., directly after harvest (unripe) and after a commercial cold storage and ripening regime (ripe). The phenolic composition of South African plums varied greatly, both qualitatively and quantitatively, between cultivars and selections. Neochlorogenic acid, cyanidin-3-O-glucoside and quercetin-3-O-glucoside were the predominant hydroxycinnamic acid, anthocyanin and flavonol, respectively, although not present in all plums. The flavan-3-ols, (+)-catechin, (−)-epicatechin and procyanidins B1 and B2, were present in all plums. Red-fleshed plums tended to display higher TAC and TPC than yellow-fleshed plums. The flavan-3-ol content was highly correlated with TAC. The effect of harvest season was cultivar-dependent, but cultivar differences were not obscured. In terms of maturity stage, the ripe fruits tended to contain higher levels of anthocyanins and some flavonol compounds, although the TPC and TAC were not affected in most cases. South African plums, especially the red-fleshed selections PR04-32 and PR04-35, were shown to provide generally high TAC and TPC compared to literature values
Some Studies on the Forming of Anisotropic Metals
No full textTitle: Some Studies on the Forming of Anisotropic Metals, Author: Ronald D. Venter, Location: ThodeThe diffuse and local inst ability criteria associated with sheet
metal forming limits are investigated for materials having a wide range
of properties. The results are compared with available experimental data.
An alternate method based on the pre-existence of an initial inhomogeneity
or weakness within the material is developed. The straining paths
which are dependent upon the particular applied stress ratio are
presented and the results correlated with experimental limit strains
obtained from the hydrostatic bulging of aluminum diaphragms in
circular and elliptical dies. A method based on the finite difference technique is developed
for the construction of slip-line fields when the material has a
defined degree of anisotropy. Solutions for the indentation of semi-infinite and finite depth anisotropic media are developed and
compared with the results obtained from the indentation of aluminum;
specimens for which the degree of anisotropy is evaluated from yield
stress considerations. The solutions are extended to include the
extrusion of anisotropic materials and the approximate, but simpler,
upper bound limits. The analogue between planeplane strain slip-line field
solutions and the collapse loads associated with flat plates are
investigated for anisotropic materials .ThesisDoctor of Philosophy (PhD
Characterisation of Phenolic Compounds in South African Plum Fruits (Prunus salicina Lindl.) using HPLC Coupled with Diode-Array, Fluorescence, Mass Spectrometry and On-Line Antioxidant Detection
No full textPhenolic compounds are abundant secondary metabolites in plums, with potential health benefits believed to be due to their antioxidant activity, amongst others. Phenolic characterisation of South African Prunus salicina Lindl. plums is necessary to fully evaluate their potential health benefits. An HPLC method using diode-array detection (DAD) for quantification of phenolic compounds was improved and fluorescence detection (FLD) was added for quantification of flavan-3-ols. Validation of the HPLC-DAD-FLD method showed its suitability for quantification of 18 phenolic compounds, including flavan-3-ols using FLD, and phenolic acids, anthocyanins and flavonols using DAD. The method was suitable for characterisation of the phenolic composition of 11 South African plum cultivars and selections, including various types with yellow and red skin and flesh. The method was used in conjunction with mass spectrometry (MS) to identify 24 phenolic compounds. Neochlorogenic acid and cyanidin-3-O-glucoside were the major compounds in most of the plums, while cyanidin-3-O-glucoside was absent in Sun Breeze plums with yellow skin and flesh. Post-column on-line coupling of the ABTS•+ scavenging assay with HPLC-DAD enabled qualitative evaluation of the relative contribution of individual phenolic compounds to the antioxidant activity. The flavan-3-ols, neochlorogenic acid and cyanidin-3-O-glucoside displayed the largest antioxidant response peaks
A Package Integratable Six Port Reflectometer for RF Power Devices
No full textSemiconductor power devices have a growing popularity in industrial, scientific and medical (ISM) band applications, such as microwave-heating, drying and plasma generation. A distinguishable property of these applications is the relentless pursuit of reliability, ruggedness, or the ability to withstand a mismatched loading condition without failure. Mismatch detection right at device output, preferably integrated in package, could provide critical information to avoid device breakdown and to enable performance optimization. In this work, the in-package mismatch detection and load monitoring is enabled by a specially designed six-port reflectometer. Compared with conventional reflection measurement techniques based on heterodyne receivers, the proposed design is passive, simple, compact and inexpensive. A hardware prototype is implemented with a size of 36 mm2. Loading conditions over the entire Smith chart are generated by a calibrated active-load-pull system and measured by the proposed system, yielding a root-mean-square error below -32 dB full-scale. This compact reflectometer enables the in-package accurate mismatch detection for the first time. The result of this study has been accepted for publication in the 2014 International Microwave Symposium, and nominated to be a finalist for its annual best paper award.MicroelectronicsMicroelectronics & Computer EngineeringElectrical Engineering, Mathematics and Computer Scienc
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